Creat membership Creat membership
Sign in

Forgot password?

Confirm
  • Forgot password?
    Sign Up
  • Confirm
    Sign In
home > search

Now showing items 1 - 16 of 22

  • Paleo‐productivity in the SW Pacific Ocean during the early Holocene climatic optimum

    Bostock, H.C.   Prebble, J.G.   Cortese, G.   Hayward, B.   Calvo, E.   Quirós‐Collazos, L.   Kienast, M.   Kim, K.  

    Download Collect
  • On the sedimentological origin of down-core variations of bulk sedimentary nitrogen isotope ratios

    Kienast, M.   Higginson, M. J.   Mollenhauer, G.   Eglinton, T. I.   Chen, M.-T.   Calvert, S. E.  

    Download Collect
  • Synchroneity of meltwater pulse 1a and the B?lling warming: New evidence from the South China Sea

    Kienast, M.   Hanebuth, T.J.J.   Pelejero, C.   Steinke, S.  

    Download Collect
  • Alkenone unsaturation in surface sediments from the eastern equatorial Pacific: Implications for SST reconstructions

    Kienast, M.   MacIntyre, G.   Dubois, N.   Higginson, S.   Normandeau, C.   Chazen, C.   Herbert, T. D.  

    Download Collect
  • A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific: Evidence of a deepening thermocline?

    Kienast, M.   Lehmann, M. F.   Timmermann, A.   Galbraith, E.   Bolliet, T.   Holbourn, A.   Normandeau, C.   Laj, C.  

    Sedimentary delta(15)N records from the oligotrophic western equatorial Pacific (WEP) off Mindanao show that late Holocene sedimentary delta(15)N is substantially lower than that of the early Holocene, following a gradual >3 parts per thousand decrease that occurred between 7 and 3 kyrs ago. Analyses of modem day nitrate isotope profiles from the same region indicate the sensitivity of the WEP N pools towards (1) the advection of (15)N-enriched nitrate from the Eastern Equatorial Pacific (EEP) by the North Equatorial Current (NEC) and the Mindanao Current in subsurface waters and, (2) at shallow depths, the input of new and (15)N-depleted nitrate through N, fixation. We suggest that the Holocene decrease in sedimentary delta(15)N reflects a diminished relative input of (15)N-enriched nitrate to the surface biota, either through an increase of regional nitrogen fixation, a change in nitrate consumption along the advective path of nitrate supply, or a decrease in the vertical Supply Of (15)N-enriched nitrate from the NEC. The latter mechanism is consistent with a Holocene deepening of the WEP nitracline/thermocline. Citation: Kienast, M., M. F. Lehmann, A. Timmermann, E. Galbraith, T. Bolliet, A. Holboum, C. Normandeau, and C. Laj (2008), A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific: Evidence of a deepening thermocline?, Geophys. Res. Lett,, 35, L23610, doi: 10.1029/2008GL035464.
    Download Collect
  • Hausens \"scheltliet\" (M F 47, 33) und \"der sumer von triere\"by Richard Kienast;Das Hartmann-Liederbuch C2by Richard Kienast

    Review by: David Blamires  

    Download Collect
  • Labor Economics: Wages, Employment, and Trade Unionismby F. Ray Marshall; Allan M. Cartter;Readings in Labor Economics and Labor Relationsby Richard L. Rowan;The Practice of Collective Bargainingby Edwin F. Beal; Edward D. Wickersham; Philip K. Kienast

    Review by: Keith E. Bernard  

    Download Collect
  • Metamorphic evolution of the Tethyan Himalayan flysch in SE Tibet

    Dunkl, I.   Antolin, B.   Wemmer, K.   Rantitsch, G.   Kienast, M.   Montomoli, C.   Ding, L.   Carosi, R.   Appel, E.   El Bay, R.   Xu, Q.   Von Eynatten, H.  

    The metamorphic conditions and the age of thermal overprint were determined in metapelites, metaarenites and metabasites of the Tethyan Himalayan Sequence (THS) in SE Tibet using Kubler Index and vitrinite reflectance data and applying thermobarometrical (Thermocalc and PERPLEX) and geochronological methods (illite/muscovite K-Ar and zircon and apatite (U-Th)/ He chronology). The multiple folded thrust pile experienced a thermal overprint reaching locally peak conditions between the diagenetic stage (c. 170 degrees C) and the amphibolite facies (c. 600 degrees C at 10 kbar). Burial diagenesis and heating due to Early Cretaceous dyke emplacement triggered the growth of illite in the metapelites. Eocene collision-related peak metamorphic conditions have been reached at c. 44 Ma. During collision the different tectonic blocks of the THS were tectonically buried to different structural levels so that they experienced maximum greenschist to amphibolite facies metamorphism. Later, during Oligocene to Miocene times the entire THS underwent anchi- to epizonal metamorphic conditions, probably associated to continuous deformation in the flysch fold-thrust-system. This period terminated at c. 24-22 Ma. Adjacent to the north Himalayan metamorphic domes, the base of the THS was metamorphosed during Miocene times (c. 13 Ma). Post-metamorphic cooling below c. 180 degrees C lasted until Late Miocene and took place at different times.
    Download Collect
  • Constraints on the magnitude and patterns of ocean cooling at the Last Glacial Maximum RID B-9277-2009 RID C-9004-2009 RID D-1653-2010

    Waelbroeck, C.   Paul, A.   Kucera, M.   Rosell-Mele, A.   Weinelt, M.   Schneider, R.   Mix, A. C.   Abelmann, A.   Armand, L.   Bard, E.   Barker, S.   Barrows, T. T.   Benway, H.   Cacho, I.   Chen, M. -T.   Cortijo, E.   Crosta, X.   de Vernal, A.   Dokken, T.   Duprat, J.   Elderfield, H.   Eynaud, F.   Gersonde, R.   Hayes, A.   Henry, M.   Hillaire-Marcel, C.   Huang, C. -C.   Jansen, E.   Juggins, S.   Kallel, N.   Kiefer, T.   Kienast, M.   Labeyrie, L.   Leclaire, H.   Londeix, L.   Mangin, S.   Matthiessen, J.   Marret, F.   Meland, M.   Morey, A. E.   Mulitza, S.   Pflaumann, U.   Pisias, N. G.   Radi, T.   Rochon, A.   Rohling, E. J.   Sbaffi, L.   Schaefer-Neth, C.   Solignac, S.   Spero, H.   Tachikawa, K.   Turon, J. -L.  

    Observation-based reconstructions of sea surface temperature from relatively stable periods in the past, such as the Last Glacial Maximum, represent an important means of constraining climate sensitivity and evaluating model simulations(1). The first quantitative global reconstruction of sea surface temperatures during the Last Glacial Maximum was developed by the Climate Long-Range Investigation, Mapping and Prediction (CLIMAP) project in the 1970s and 1980s (refs 2,3). Since that time, several shortcomings of that earlier effort have become apparent(4). Here we present an updated synthesis of sea surface temperatures during the Last Glacial Maximum, rigorously defined as the period between 23 and 19 thousand years before present, from the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project(5). We integrate microfossil and geochemical reconstructions of surface temperatures and include assessments of the reliability of individual records. Our reconstruction reveals the presence of large longitudinal gradients in sea surface temperature in all of the ocean basins, in contrast to the simulations of the Last Glacial Maximum climate available at present(6,7).
    Download Collect
  • Testing the silica leakage hypothesis with sedimentary opal records from the eastern equatorial Pacific over the last 150 kyrs

    Kienast, S. S.   Kienast, M.   Jaccard, S.   Calvert, S. E.   Francois, R.  

    We have measured Th-230-normalized opal fluxes in several cores from the eastern equatorial Pacific (EEP) to test the validity of the "silica leakage'' hypothesis, which purports that redistribution of silicic acid from the Southern Ocean to the low latitudes was responsible for a significant portion of the reduction in atmospheric carbon dioxide (CO2) during the last glacial period. The silica leakage hypothesis predicts higher opal fluxes in the EEP and lower opal fluxes in the Southern Ocean during periods of low atmospheric CO2. These predictions are not borne by the sedimentary record during glacial oxygen isotope stage 2 (OIS 2, 13 - 27 kyrs B. P.). However, we find a prominent opal flux maximum in the EEP in the middle of OIS 3 (ca. 40 - 60 kyrs BP) coinciding with low opal fluxes in several cores from the subantarctic zone. This observation is consistent with silica leakage from the Southern Ocean to the equatorial upwelling region during OIS 3, when both low dust flux and extended sea ice could have contributed to limiting diatom productivity in the Southern Ocean. Since this event is not associated with a clear minimum in the Vostok ice record of CO2, its impact on atmospheric CO2 appears to be small.
    Download Collect
  • Paleoproductivity in the SW Pacific Ocean During the Early Holocene Climatic Optimum

    Bostock, H. C.   Prebble, J. G.   Cortese, G.   Hayward, B.   Calvo, E.   Quiros-Collazos, L.   Kienast, M.   Kim, K.  

    The oceans are warming, but it is unclear how marine productivity will be affected under future climate change. In this study we examined a wide range of paleoproductivity proxies along a latitudinal transect (36-58 degrees S) in the SW Pacific during the early Holocene climatic optimum, to explore regional patterns of productivity in a slightly warmer-than-present world. During the early Holocene there is a small increase in productivity in the subtropical waters, no change at the subtropical frontal zone, and conflicting evidence in records immediately south of the subtropical front, where an increase is inferred from one core site, but not at the other. Evidence for an increase in productivity in Antarctic Surface Waters, south of the polar front, is also equivocal. We infer a small increase in productivity in subtropical waters, and the ocean just south of the subtropical front was associated with changes in the ocean circulation of the SW Pacific, driven by changes in the Southern Hemisphere Westerly Winds split jet structure in this region. The relatively modest warming during the early Holocene climatic optimum in the SW Pacific indicates that this time period may provide an analog for future productivity for the midcentury (2055) under Intergovernmental Panel on Climate Change Representative Concentration Pathway 8.5 or for the end of the century (2100) under Representative Concentration Pathway 4.5. However, higher-resolution, downscaled models, with realistic Southern Hemisphere Westerly Winds, will be necessary to forecast future productivity for this oceanographically complex region.
    Download Collect
  • D. Kienast, Die spontane Vegetation der Stadt Kassel. 410 S., 63 Tab. mit Originalaufn. von ca. 900 Pflanzen- u. 270 Sigmagesellschaften, übersichtstab. u. Verbreitungskarten, 2 Kartenbeilagen. Schr.-R. Urbs et Regio, H. 10, 1978. ISBN 3-88122-037-2. Preis: 20,— DM; zu beziehen über die Gesamthochschul-Bibliothek der Gesamthochschule Kassel, M?nchebergstr. 19, 3500 Kassel oder den Buchhandel

    P. Gutte  

    Download Collect
  • A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific: Evidence of a deepening thermocline? RID F-4977-2011

    Kienast, M.   Lehmann, M. F.   Timmermann, A.   Galbraith, E.   Bolliet, T.   Holboum, A.   Normandeau, C.   Laj, C.  

    Sedimentary delta(15)N records from the oligotrophic western equatorial Pacific (WEP) off Mindanao show that late Holocene sedimentary delta(15)N is substantially lower than that of the early Holocene, following a gradual >3 parts per thousand decrease that occurred between 7 and 3 kyrs ago. Analyses of modem day nitrate isotope profiles from the same region indicate the sensitivity of the WEP N pools towards (1) the advection of (15)N-enriched nitrate from the Eastern Equatorial Pacific (EEP) by the North Equatorial Current (NEC) and the Mindanao Current in subsurface waters and, (2) at shallow depths, the input of new and (15)N-depleted nitrate through N, fixation. We suggest that the Holocene decrease in sedimentary delta(15)N reflects a diminished relative input of (15)N-enriched nitrate to the surface biota, either through an increase of regional nitrogen fixation, a change in nitrate consumption along the advective path of nitrate supply, or a decrease in the vertical Supply Of (15)N-enriched nitrate from the NEC. The latter mechanism is consistent with a Holocene deepening of the WEP nitracline/thermocline. Citation: Kienast, M., M. F. Lehmann, A. Timmermann, E. Galbraith, T. Bolliet, A. Holboum, C. Normandeau, and C. Laj (2008), A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific: Evidence of a deepening thermocline?, Geophys. Res. Lett,, 35, L23610, doi: 10.1029/2008GL035464.
    Download Collect
  • The Role of Uncertainty in Estimating Lead/Lag Relationships in Marine Sedimentary Archives:A Case Study From the Tropical Pacific

    Khider, D.   Ahn, S.   Lisiecki, L. E.   Lawrence, C. E.   Kienast, M.  

    Understanding the mechanisms behind any changes in the climate system often requires establishing the timing of events imprinted on the geological record. However, these proxy records are prone to large uncertainties, which may preclude meaningful conclusions about the relative timing of events. In this study, we put forth a framework to estimate the uncertainty in phase relationships inferred from marine sedimentary records. The novelty of our method lies in the accounting of the various sources of uncertainty inherent to paleoclimate reconstruction and timing analysis. Specifically, we use a Monte Carlo process allowing sampling of possible realizations of the time series as functions of uncertainties in time, the climate proxy, and the identification of the termination timing. We then apply this technique to 15 published sea surface temperature records from the equatorial Pacific to evaluate whether we observed any significant changes in the termination timing between the east and the west. We find that the uncertainty on the relative timing estimates is on the order of several thousand years and mainly stems from age model uncertainty (90%). However, even small differences in mean termination timings can be detected with a sufficiently large number of samples. Improvements in the dating of sediment records provide an opportunity to reduce uncertainty in studies of this kind.
    Download Collect
  • Synchronous tropical South China Sea SST change and Greenland warming during deglaciation

    Kienast, M.   Steinke, S.   Stattegger, K.   Calvert, S.E.  

    The tropical ocean plays a major rocircle in global climate. It is therefore crucial to establish the precise phase between tropical and high-latitude climate variability during past abrupt climate events in order to gain insight into the mechanisms of global climate change. The authors present alkenone sea surface temperature (SST) records from the tropical South China Sea that show an abrupt temperature increase of at least 1 degC at the end of the last glacial period. Within the recognized dating uncertainties, this SST increase is synchronous with the Boslashlling warming observed at 14.6 thousand years ago in the Greenland Ice Sheet Project 2 ice core
    Download Collect
  • Hausens 'scheltliet' (M F 47, 33) und 'der sumer von triere'by Richard Kienast;Das Hartmann-Liederbuch C2by Richard Kienast

    Review by: David Blamires  

    Download Collect
1 2

Contact

If you have any feedback, Please follow the official account to submit feedback.

Turn on your phone and scan

Submit Feedback